The present invention relates to an anti-tumour substance obtained by bonding an anti-tumour agent to human immunoglobulin and a process for preparing the same.
Recently, with the development of immunochemistry, a large number of tumour-related antigen have been discovered and the tumour-specific antibody which selectively bonds to these tumour-related antigens has been developed. Further, trials are now under way wherein an anti-tumour agent is bonded to the tumour-specific antibody and the thus formed substance is administered to the patient suffering from the tumour for transferring the substance collectively to the portion of the tumour. In this trial, the tumour-specific antibody is prepared by a technique of immunizing a rabbit, horse and sheep with the tumour cells or the tumour-related antigen and is obtained from the serum of the thus immunized animal as an immunoglobulin fraction. In more recent years, after immunizing a mouse with the tumour cells or the tumour-related antigen, the antigen-producing cells are taken out from the mouse and the thus collected cells are subjected to cell fusion with the mouse-myleloma cells such as NS-1, thereby obtaining the monochronal cells producing anti-tumour antibody, and the anti-tumour antibody is taken out from the cells.
Although the trials are carried out with the anti-tumour antibody itself or the substance produced by bonding a certain cytotoxic substance to the anti-tumour antibody, the method has not been carried out practically, because the anti-tumour antibody is a heteroprotein to human, since the antibody has been obtained by immunizing a heterospecific animal. Namely, in the case where the antibody obtained from a heterospecific animal is administered to a person, the occurrence of a serum disease such as anaphylaxis, etc. on the second and successive administration cannot be evitable. In short, such an anti-tumour antibody can be used only once, and such a fact is the largest demerit of the method. It is necessary to use a homospecific antibody for overcoming the demerit, and the monochronal antibody prepared by using human lymphocytes is the ideal, however, such an antibody has not been provided.
Accordingly, it has been necessary for improving the demerits and solving the affairs concerning the practicality of such a method to investigate the homospecific antibodies and select those assembling to the tumour cells.
The present inventors, as a result of examination of the distribution of the various .sup.125 I-labelled antibodies in living body, have found that the general natural antibodies arrive at the portion of tumour and remain there for a long period of time and accordingly, the present inventors have known that in the case where after bonding an anti-tumour agent to the immunoglobulin, the thus obtained substance is administered to the cancer-bearing individual, the anti-tumour agent remains for a long period in the portion of the tumour, thereby exhibiting the anti-tumour effect. The present invention has been attained on these findings.
The anti-tumour substance obtained by bonding an anti-tumour agent to human immunoglobulin according to the present invention has the largest specificity and merit in that the anti-tumour substance obtained by bonding the anti-tumour agent to human immunoglobulin can be frequently administered as compared to the known product produced by bonding the anti-tumour agent to the anti-tumour antibody derived from the animal of different species from human, and remains at the portion of tumour for a long period of time.
Accordingly, the present invention provides a new type of medicines, which contains the anti-tumour substance produced by bonding an anti-tumour agent to human immunoglobulin and is highly practical.